FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Securities:
Held to maturity	$ 95,010	$ 100,041
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	327,405	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	1,013	2,026
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Cash surrender value on life insurance	0	0
Derivative instruments	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest rate lock commitments
Securities:
Derivative instruments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Demand deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Savings deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Time deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Forward commitments
Securities:
Derivative instruments	0
Financial liabilities:
Derivative liabilities	0	0
Level 2
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	7,448,923	6,125,949
Held to maturity	95,010	100,041
Other investments	83,332	75,523
Loans held for sale	37,078	57,949
Loans, net	9,720,384	9,735,181
Cash surrender value on life insurance	190,576	187,664
Derivative instruments	26,232	44,102
Financial liabilities:
Short term borrowings	265,620	167,872
Other borrowings	372,902	458,806
Derivative liabilities	27,782	51,962
Level 2 | Interest rate lock commitments
Securities:
Derivative instruments	0	0
Level 2 | Demand deposits
Financial liabilities:
Deposits	6,537,722	5,688,810
Level 2 | Savings deposits
Financial liabilities:
Deposits	8,416,204	8,019,704
Level 2 | Time deposits
Financial liabilities:
Deposits	1,070,957	1,273,468
Level 2 | Forward commitments
Securities:
Derivative instruments	278
Financial liabilities:
Derivative liabilities	59	697
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	0	0
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	38,179	34,488
Cash surrender value on life insurance	0	0
Derivative instruments	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Interest rate lock commitments
Securities:
Derivative instruments	1,204	1,827
Significant Unobservable Inputs (Level 3) | Demand deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Savings deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Time deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Forward commitments
Securities:
Derivative instruments	0
Financial liabilities:
Derivative liabilities	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial and industrial
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Owner occupied commercial real estate
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-owner occupied commercial real estate
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate construction
Securities:
Loans, net	0	0
Commercial and industrial | Level 2 | Commercial and industrial
Securities:
Loans, net	2,488,044	2,379,785
Commercial and industrial | Level 2 | Paycheck Protection Program ("PPP")
Securities:
Loans, net	409,247	957,785
Commercial and industrial | Level 2 | Owner occupied commercial real estate
Securities:
Loans, net	2,115,459	1,739,523
Commercial and industrial | Level 2 | Non-owner occupied commercial real estate
Securities:
Loans, net	1,993,612	1,887,306
Commercial and industrial | Level 2 | Real estate construction
Securities:
Loans, net	803,298	849,224
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Securities:
Loans, net	10,270	11,256
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	0	0
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Owner occupied commercial real estate
Securities:
Loans, net	3,552	5,874
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Non-owner occupied commercial real estate
Securities:
Loans, net	15,212	4,907
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Real estate construction
Securities:
Loans, net	0	0
Agricultural and agricultural real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Agricultural and agricultural real estate | Level 2
Securities:
Loans, net	671,556	685,278
Agricultural and agricultural real estate | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	9,145	12,451
Residential real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Residential real estate | Level 2
Securities:
Loans, net	831,021	828,366
Residential real estate | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	0	0
Consumer | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Consumer | Level 2
Securities:
Loans, net	408,147	407,914
Consumer | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents	327,405	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	7,449,936	6,127,975
Held to maturity	85,354	88,839
Other investments	83,332	75,253
Loans held for sale	37,078	57,949
Loans, net	9,737,374	9,891,445
Cash surrender value on life insurance	190,576	187,664
Derivative instruments	26,232	44,102
Financial liabilities:
Short term borrowings	265,620	167,872
Other borrowings	371,765	457,042
Derivative liabilities	27,782	51,962
Carrying Amount | Interest rate lock commitments
Securities:
Derivative instruments	1,204	1,827
Carrying Amount | Demand deposits
Financial liabilities:
Deposits	6,537,722	5,688,810
Carrying Amount | Savings deposits
Financial liabilities:
Deposits	8,416,204	8,019,704
Carrying Amount | Time deposits
Financial liabilities:
Deposits	1,068,317	1,271,391
Carrying Amount | Forward commitments
Securities:
Derivative instruments	278
Financial liabilities:
Derivative liabilities	59	697
Carrying Amount | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	2,510,461	2,495,981
Carrying Amount | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	409,247	957,785
Carrying Amount | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,116,099	1,756,405
Carrying Amount | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	1,998,372	1,900,608
Carrying Amount | Commercial and industrial | Real estate construction
Securities:
Loans, net	790,303	843,140
Carrying Amount | Agricultural and agricultural real estate
Securities:
Loans, net	678,344	707,397
Carrying Amount | Residential real estate
Securities:
Loans, net	831,118	828,507
Carrying Amount | Consumer
Securities:
Loans, net	403,430	401,622
Estimated Fair Value
Financial assets:
Cash and cash equivalents	327,405	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	7,449,936	6,127,975
Held to maturity	95,010	100,041
Other investments	83,332	75,523
Loans held for sale	37,078	57,949
Loans, net	9,758,563	9,769,669
Cash surrender value on life insurance	190,576	187,664
Derivative instruments	26,232	44,102
Financial liabilities:
Short term borrowings	265,620	167,872
Other borrowings	372,902	458,806
Derivative liabilities	27,782	51,962
Estimated Fair Value | Interest rate lock commitments
Securities:
Derivative instruments	1,204	1,827
Estimated Fair Value | Demand deposits
Financial liabilities:
Deposits	6,537,722	5,688,810
Estimated Fair Value | Savings deposits
Financial liabilities:
Deposits	8,416,204	8,019,704
Estimated Fair Value | Time deposits
Financial liabilities:
Deposits	1,070,957	1,273,468
Estimated Fair Value | Forward commitments
Securities:
Derivative instruments	278
Financial liabilities:
Derivative liabilities	59	697
Estimated Fair Value | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	2,498,314	2,391,041
Estimated Fair Value | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	409,247	957,785
Estimated Fair Value | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,119,011	1,745,397
Estimated Fair Value | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	2,008,824	1,892,213
Estimated Fair Value | Commercial and industrial | Real estate construction
Securities:
Loans, net	803,298	849,224
Estimated Fair Value | Agricultural and agricultural real estate
Securities:
Loans, net	680,701	697,729
Estimated Fair Value | Residential real estate
Securities:
Loans, net	831,021	828,366
Estimated Fair Value | Consumer
Securities:
Loans, net	$ 408,147	$ 407,914